High-Frequency 3d Geomorphic Observation Using Hourly Terrestrial Laser Scanning Data of a Sandy Beach

Abstract

<p><strong>Abstract.</strong> Geomorphic processes occur spatially variable and at varying magnitudes, frequencies and velocities, which poses a great challenge to current methods of topographic change analysis. For the quantification of surface change, permanent terrestrial laser scanning (TLS) can generate time series of 3D point clouds at high temporal and spatial resolution. We investigate how the temporal interval influences volume change observed on a sandy beach regarding the temporal detail of the change process and the total volume budget, on which accretion and erosion counteract. We use an hourly time series of TLS point clouds acquired over six weeks in Kijkduin, the Netherlands. A raster-based approach of elevation differencing provides the volume change over time per square meter. We compare the hourly analysis to results of a three- and six-week observation period. For the larger period, a volume increase of 0.3 m<sup>3</sup>/ m<sup>2</sup> is missed on a forming sand bar before it disappears, which corresponds to half its volume. Generally, a strong relationship is shown between observation interval and observed volume change. An increase from weekly to daily observations leads to a five times larger volume change quantified in total. Another important finding is a temporally variable measurement uncertainty in the 3D time series, which follows the daily course of air temperature. Further experiments are required to fully understand the effect of atmospheric conditions on high-frequency TLS acquisition in beach environments. Continued research of 4D geospatial analysis methods will enable automatic identification of dynamic change and improve the understanding of geomorphic processes.</p>

Coastal Change Patterns from Time Series Clustering of Permanent Laser Scan Data

“…However, the steep rise of the centroid from cluster 5 allows to conclude that the cause of this sudden accretion is not natural. The information found by Anders et al (2019) for the research on their study, confirms the coinciding bulldozer works.…”

“…To allow for a comparison of the clusters with a sort of ground truth, we selected a test area at the bottom of the footpath. In this area a pile of sand was accumulated by a bulldozer, after the entrance to the path was covered with lots of sand during the storm, as found by Anders et al (2019). We chose two time stamps for illustration and show the elevation before the bulldozer activity on 12 January, after the bulldozer activity on 16 January and the difference between the elevations on these two days in Figure 7.…”

3d Point Errors and Change Detection Accuracy of Unmanned Aerial Vehicle Laser Scanning Data

“…They introduced a spatio-temporal LOD, which considers system geometry, point density, atmospheric effects and surface roughness, and also includes the frequency of available scans. Anders et al (2019) investigated dynamics of a sandy beach by analysing high-frequency long-range TLS time series. They defined the LOD after Kromer et al (2017) by considering TLS system measurement accuracy, influence of scan geometry, registration and georeferencing errors, surface roughness, and atmospheric parameters.…”

Automated and Permanent Long-Range Terrestrial Laser Scanning in a High Mountain Environment: Setup and First Results

“…To our knowledge, there Subsequently, the permanent installation of TLSs is worldwide rare. We are aware of installations of RIEGL VZ-2000 laser scanners at beaches to investigate coastal dynamics in the Netherlands (Vos et al, 2017;Anders et al, 2019) and in Belgium (Deruyter et al, 2020). This research is similar to laser scanning at glacierized environments, because sandy coast dynamics are comparable with snow cover dynamics as it occurs on high spatiotemporal scales (Comola and Lehning, 2017;Cowell et al, 2003).…”